This invention relates to a method and apparatus for protecting sensitive electronic or magnetic memories, logic circuitry, and the like in modern business machines or computer equipment from destruction, disruption or errors which could result from spurious impulses generated by an electrostatic discharge from the equipment operator's body to the equipment while simultaneously insuring that the equipment operator does not experience a harmful or annoying electrical shock.
Most persons have probably noted that a charge of static electricity may be generated by a person walking across a floor covered by carpeting made of certain synthetic materials, or when wearing clothing manufactured of certain synthetic fibers. Under conditions of relatively low humidity, a relatively large electrical potential may be developed, and when the person extends his fingers or hands while attempting to touch an object at a lower electrical potential, current flows from the extremeties thereof causing the person to experience a shocking sensation. Although the shock experienced is often more annoying than harmful, it is desirable to provide devices for eliminating the shock.
Several attempts have been made in the prior art for minimizing the shock experienced by such a person. Most of the attempts have employed discharging devices which can be used in conjunction with doorknobs, switches, push buttons and the like which can operate to discharge the accumulated charge of static electricity stored on the person's body without substantial discomfort to the charged person. U.S. Pat. No. 3,621,164 to Stanley Backer, and U.S. Pat. No. 3,099,774 to John J. Crane are examples of such prior art systems and usually employ a means for dissipating the charge via a spark discharge across an air gap or through a resistor. U.S. Pat. No. 3,780,345 to Ernest Earman, Jr. provides a static electricity de-shocker which employs a 10 megaohm resistor to intercept, arrest or reduce the static discharge to a non-shocking state or degree.
All of the systems of the prior art are aimed primarily at reducing the shock experienced by the persons who have accumulated the static charge. Such systems employ a spark discharge across an air gap or a direct contact discharge through a high valued resistor. None of these systems completely eliminate discomfort to the charged person and none of these prior art systems serve to protect anything other than the charged person.
Many of today's modern business machines, mini-computers, computer terminals, computers and the like, contain sensitive electronic and/or magnetic circuits and/or memories. A static discharge which could result if the machine operator's body was at a substantially different electrical potential from that of the machine were to make contact or near contact with the machine could produce a spurious signal which could change the state of various logic circuits or the contents of various electronic or magnetic memories so as to cause errors in the machine's operation or otherwise damage the machine itself.